Prior to the instant invention umbrellas have included structure comprising canopies which are principally supported by ribs butressed by hinged chords. Prior attempts to eliminate the ribs have resulted in generally unsatisfactory umbrella constructions which fail or inadequately serve the user confronted with the necessity of opening and closing the umbrella and to protect the user in times of inclement weather. Prior umbrella constructions are depicted in the following U.S. Patents to Wilson, U.S. Pat. No. 3,186,421; Spiro, U.S. Pat. No. 1,833,004; and dePolo, U.S. Pat. No. 4,084,600; as well as the Russian Patent No. 479468 and the French Patent to Alan Philip Sasseen No. 2,403,760.
It is to be desired that umbrellas protect users under windy conditions. Wind can strike an umbrella from any direction. Most winds which affect an umbrella come down on the open umbrella canopy or blow up against the underside of the open canopy.
Traditional umbrellas comprising canopies which are principally supported by flexible ribs extending radially from the staff at their inner ends to the outer margin of the canopy at their outer ends which ribs are each buttressed at an intermediate location along its length by a hinged link or chord which serves to make the innermost portions of the rib rigid and leave the outermost portion of the rib flexible. Such prior constructions are prone to having the canopy turned inside out during an updraft. The triangulation afforded by the buttressing hinged link or chord does not extend to the margin of the canopy. Also, because the inner part of the canopy is buttressed while the outer part is not, the umbrella canopy when open has limited flexibility in the face of a down draft which may cause the umbrella frame to break or the canopy fabric to tear away from the frame.
Prior umbrellas which utilize a series of chords which extend from the staff to the outer margin of the canopy and no ribs are either so rigid that the fabric will tear away from the frame in a heavy wind unless additional cables so the like are installed in the hem or peripheral margin of the canopy or of such construction which lacks the quality of desired protection as heretofore described.
In accordance with the instant invention, the construction is such that the canopy frame is relatively rigid when faced with an updraft and triangulation extends from the staff all the way outwardly to the margin of the canopy. A stop limits the angle of the chords so as to keep an updraft from turning the canopy inside out. In a down draft, the canopy frame is all flexible and a strong down draft will close the umbrella insuring that the fabric will not tear from the frame.
It is an object of the instant invention to provide a strong, stable, ribless construction in which the conventional ribs that normally support the canopy are omitted and wherein radial chords influenced by spring pressure serve to maintain the canopy under tension and wherein guide means are provided to control the inner ends of the chords when the umbrella is almost or completely closed.
Other objects and the nature and advantages of the invention will become apparent from the following description and exposition taken with the accompanying drawings.